An underwater spark is able to induce a cavitation bubble, and this principle has been utilized to make cavitation bubble generators for several decades. In this paper, an improved instrument for generating spark-induced cavitation bubbles is described in detail. The voltage time history inside the instrument is measured to show the working process and principle. Cavitation bubbles are generated by the instrument and recorded by a high-speed camera. The radius time history of the bubble is obtained using an image processing algorithm. The ratio of its minimum radius to its maximum radius reaches ~0.2, which indicates that there is little undissolved gas in the bubble. With the radius time history, the velocity fields around the bubbles were calculated by the 1D continuity flow equation, and the pressure fields were calculated by the 1D Euler equation. One cavitation bubble is chosen and discussed in detail. The velocity and pressure on the bubble interface achieve their maximums (~25 m/s and ~1.2 MPa, respectively) at the same time, when the radius is at its minimum (~1 mm). Some statistical results are also presented to show the effect of the instrument.

Cavitation erosion is a fundamental concern in many fields of engineering, e.g. the flow separation zone in high speed flow and the blade area of hydraulic machinery. However, the influence of the physical characteristics of the environmental medium in these engineering facilities on cavitation erosion is still unclear. In this paper, we adopted underwater low-voltage discharge technology to generate cavitation bubbles, and studied the mesoscale causes of material erosion in solutions with different surface tensions. It is found that with the decrease of liquid surface tension, the radial velocity of cavitation bubbles decreases significantly during the shrinkage of the cavitation bubble and the minimum radius to which the cavitation bubble shrinks increases, the micro-jet generated by the cavitation bubble develops more slowly, and the impact strength of cavitation bubble collapses on the wall decreases. The findings reveal new physical mechanisms of the cavitation-induced material erosion in liquids with different surface tensions at the macroscopic level. These will provide significant guidance for cavitation prevention in various applications such as aeration cavitation-alleviation, hydraulic machinery, ultrasonic cleaning and the medical industry.

Cavitation phenomena widely exist in many fields such as medical treatment, chemical engineering, and hydraulic engineering. The boundary properties have a great influence on the collapse characteristics of a cavitation bubble. The interaction between a cavitation bubble and a boundary of different properties is an important part in the cavitation erosion mechanism. In this paper, cavitation bubbles under in-water pulse discharge and cavitation erosion under ultrasonic vibration were used to study the effect of a deformable boundary on the collapse characteristics of a cavitation bubble, which reveals the cavitation-resistance performance of different materials on the macroscopic scale. The main experimental results showed that on a deformable boundary, the cavitation bubble does not collapse toward the boundary in the later collapse stage compared with on the rigid boundary. The collapse process of the cavitation bubble is aggravated on the deformable boundary. In the condition of same cavitation strength, the cavitation's erosion loss amount on the rigid boundary material is much higher than that on the deformable boundary material. The experimental conclusions have an important reference value for the development of cavitation erosion prevention and the exploration of cavitation-resistance materials.

Understanding the mechanisms behind the cavitation erosion resistance of elastic materials is the basis for the development of new cavitation erosion resistance materials. This paper employs underwater low-voltage discharge to induce cavitation bubble, combined with high-speed photography, shadowgraph methods, and transient pressure measurement systems to experimentally investigate the evolution and intensity of shockwave from bubble collapse near elastic-rigid composite boundary. Under the condition of constant elastic material thickness, with the bubble–wall distance increasing, shockwave shape evolves from multi-layers to single-layer. The peak pressure of the shockwave shows a trend of decreasing, then increasing, and finally stabilizing with increase in the bubble–wall distance. Furthermore, it was found that the elastic-rigid composite boundary causes the shockwave to reflect twice. As the material thickness increases, the intensity of the first reflected shockwave from the elastic surface decreases initially, then increases, and eventually stabilizes. However, that of the second reflected shockwave decreases. The total energy of the two reflections at the elastic interface is less than 4% of the mechanical energy of the bubble at its maximum volume. Finally, after the energy dissipation by the two reflections and material deformation, the elastic layer substrate withstands over 70% of the total mechanical energy of the cavitation bubble. There is an optimal elastic material thickness to minimize the shockwave load on the elastic layer substrate under the condition that the elastic-rigid composite boundary does not affect the evolution of cavitation bubble shape. These findings are significant for understanding bubble dynamics near elastic-rigid composite boundaries and provide theoretical support for developing cavitation erosion-resistant materials in engineering.

The formation of a landslide dam is strongly influenced by the properties of the source debris, yet the formation interval has received less systematic attention from a material perspective than stability and breach behavior. This review synthesizes field cases, flume experiments, and numerical simulations to develop a material-centered framework that traces key source descriptors through sequential formation stages to both macroscopic geometry and inherited internal structure, two outcomes that jointly determine how a formed dam responds to overtopping, seepage, and breach. The synthesis shows that multiple material descriptors, spanning grain size distribution, grading continuity, fines fraction, density state, and water-bearing condition, jointly regulate momentum retention, energy dissipation, blockage state, and depositional structure across the formation sequence, with their combined expression recorded in the spatial organization of the dam body. To characterize this organization in a reproducible way, directional indices are proposed that capture internal structural contrasts and serve as a reference for experimental and field studies on dam stability and breach development.

Cascading failures of clustered landslide dams can intensify downstream hazards not only by increasing peak flood magnitude but also by accelerating the rise of water level immediately upstream of successive dams, thereby shortening the available response time before overtopping. This study reports large-scale flume experiments on a three-dam cascade built with identical geometry and similar soil gradation, while systematically varying longitudinal spacing and inflow discharge. The principal measured variable, $C_w\left(t\right)$, is defined here as the local forebay run-up/water-level record measured at a fixed gauge position immediately upstream of each dam. The run-up hydrographs were summarized using peak run-up $C_w^{\mathrm{m}\mathrm{a}\mathrm{x}}$, threshold-arrival time $t_a$ defined at $0.1 C_w^{\mathrm{m}\mathrm{a}\mathrm{x}}$, time to peak $t_p$, maximum rising-stage rate $S^{\mathrm{m}\mathrm{a}\mathrm{x}}$, and above-threshold duration $T$. Across ten tests (five spacing configurations under low/high discharge), peak run-up at both downstream dams consistently exceeded that at Dam1, with amplification factors relative to Dam1 of 1.11–1.45 at Dam2 and 1.13–1.42 at Dam3; Dam3 was not always higher than Dam2. Amplification was much stronger in the rising-stage dynamics: $S^{\mathrm{m}\mathrm{a}\mathrm{x}}$ increased relative to Dam1 by factors of 1.56–11.0 at Dam2 and 2.27–14.0 at Dam3, demonstrating pronounced downstream wavefront steepening. Higher discharge produced earlier threshold arrivals and peaks throughout the cascade, whereas shorter spacing generally produced more impulsive downstream responses with sharper peaks and larger rate amplification. Overall, the dataset provides stage/run-up-based constraints on cascade amplification and indicates that, within the present experimental matrix, dam spacing is the dominant geometric control on flood propagation and downstream hazard escalation.